There exists marketed devices which gauge or indicate temperature of the water flowing from a common faucet. All such devices exhibit the same problem in that the temperature must be translated from mechanical scales by the operator and provide no guided decisions for adjustment. Temperature is interpreted by reading a temperature scale and therefor the reading of the temperature is subject to error. The public, including children, the aged, and those of limited mental capacity have difficulty in reading such scales of temperature and mistakes can be easily made. Existing systems provide no direct positive feedback to the operator on which temperature control valve adjustment is required to achieve a desired fluid temperature range. Prior mechanical methods also require in-line attachment to a fluid source and many units are too sophisticated for ease of operation and calibration. Mixing valves with integral mechanical temperature scales appear in U.S. Pat. Nos. 2,171,992 and 3,960,016 and embody the general style of mechanical temperature sensor combined with control valves.
It is well known that electronic temperature sensing devices, such as thermistors, have replaced the bulb and bimetalic mechanical indicators. Electronic temperature devices are accurate, reliable and easy to signal translate into a variety of display indications, especially digital readouts. Examples of these devices are related in U.S. Pat. Nos. 3,494,196, 3,857,285 and 3,927,571. All of these patents employ resistive electronic temperature sensing which is translated and displayed by various techniques standard to the art. The devices mentioned above may include two or more signal indicators, with only one illuminated to display the intended temperature condition. However, said patents do not relate any device or fixture which directly indicates the need for particular control adjustment of a fluid mixing valve to achieve a preset fluid temperature blend. Further, neither of the disclosed methods, mixing valves with mechanical temperature indications or electronic temperature sensing contains method, means or apparatus for determining and communicating appropriate adjustment for a single or several fluid valves to achieve a proper fluid temperature range and temperature blend ratio.
These prior patents fail to disclose any fluid temperature sensing and mixing control device either mechanical or electrical which is responsive only when fluid flow is present at the sensing element. Prior art exists in fluid flow switches both mechanical and electrical with various signal translations, such as analog and digital, but such devices are concerned with flow rate or fluid content rather than conservation of electrical power in a temperature blending adjustment apparatus which in its most practical form must operate from a limited life current source such as batteries. Further, without determining flow, a great hazard exists to all such devices by presenting false or misleading readings which inturn may cause improper indications of the need for adjustment with degradation of the circuitry due to continuous operation.